It is known that during milling cutting operations the length of the cutting edge is directly related to the vibrations induced in the milling cutter and the workpiece and the energy requirements in carrying out the cutting operation. The vibrations give rise to so-called "chatter". In other words, "chatter" tends to increase with increasing length of the cutting edge.
The vibrations and consequent "chatter" arise out of the forces exerted on the cutting insert and especially on the cutting rake surface thereof by the chip which is formed and the greater the width of the chip, the greater will be the exerted forces. With a view to decreasing these vibrations and "chatter", it is known to employ milling cutters having cutting inserts with relatively short cutting edges, the inserts being so oriented with respect to the tool holder and with respect to each other that the cutting pads of the cutting edges of successive cutting inserts overlap. In this way each relatively short cutting edge gives rise to a chip of relatively narrow width, the overlap between the cutting edges of successive cutting inserts ensuring that relatively smooth milling is attained.
In practice, however, this proposal is not found to be effective, requiring as it does the careful preliminary orientation of correctly designed cutting inserts on and with respect to the tool holder.
The co-pending application disclosed a new and improved cutting insert for use with a milling cutter, which insert is, by itself, capable of achieving the desired objective of reduced "chatter" in the use of the milling cutter tool.
According to the co-pending application, there is provided a cutting insert for use with a rotary milling cutter tool and having a cutting edge defined between a cutting rake surface and a relief flank and having a base edge defined between said relief flank and a base surface;
characterised in that
said cutting edge comprises a plurality of successive component cutting edges and intermediate edges respectively located between successive component cutting edges; each component cutting edge having respective leading and trailing extremities, the trailing extremity of one component cutting edge merging with the leading extremity of a succeeding component cutting edge via an intermediate edge, said intermediate edge being directed from said trailing extremity of said one component cutting edge towards said base edge; each normal to an axis of rotation of said cutter tool which passes through a trailing extremity of one component cutting edge intersects the successive component cutting edge so that during a milling operation, successive component cutting edges overlap.
With such a cutting insert, and in view of the fact that the component cutting edges are very short, the resultant forces exerted on the cutting insert by the chips formed by these short cutting edges are relatively low and, in consequence, the degree of "chatter" encountered is minimal. Thus, in view of the relative disposition of the component cutting edges with the degree of overlapping of adjacent successive component cutting edges, it is ensured that effectively separate chips are formed of relatively low width.